An eyepiece lens for observing an image formed by an objective lens through the erect system in an enlarged manner has been known, wherein it is used in a single lens reflex camera. The eyepiece lens consists of three elements in three groups including a negative lens group (a first lens group), a positive lens group (a second lens group) and a negative lens group (a third lens group) in the order from the eyepoint side. The refracting powers of the second and third lens groups are appropriately decided. Further, aberrations are well corrected by moving the second lens group along an optical axis, whereby an image magnification is higher, and a diopter is adjustable (e.g., see the following Patent Application references 1 to 3).
[Patent Application reference 1] Japan Patent Laid open 2000-171731
[Patent Application reference 2] Japan Patent Laid open 2001-100115
[Patent Application reference 3] Japan Patent Laid open 2001-324684
With recent progression toward electronization of the cameras, various image pick-up devices have been mounted on these cameras. For example, a size of CCD used as the image pick-up device is as small as a few to a few tenths of a conventional silver halide film. Thus, as for the eyepiece lens, there is a strong demand for a higher magnification.
At the same time, in order to enhance a user's ease of use and enable an observation of an overall field to be easily, it is demanded that the eyepiece lens has a sufficiently long distance from an eyepiece lens in use to a pupil of the user (hereinafter referred to as an eye relief).
Furthermore, it is demanded that the eyepiece lens is provided with a diopter correcting function.